Display Device

ABSTRACT

A display device for improving an outcoupling efficiency of emitted light is disclosed. The display device includes a substrate, a subpixel arranged on the substrate, the subpixel including an organic light emitting diode having an emission portion that emits light, a first passivation layer disposed on the organic light emitting diode, at least one lens positioned on the first passivation layer, the at least one lens disposed in a position corresponding to the emission portion of the organic light emitting diode, a cover layer covering the at least one lens, and a second passivation layer disposed on the cover layer. A refractive index of the at least one lens is greater than a refractive index of the cover layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Republic of Korea PatentApplication No. 10-2017-0067811 filed on May 31, 2017, which areincorporated herein by reference in its entirety.

BACKGROUND Field of Technology

The present disclosure relates to a display device, and moreparticularly to a display device for improving an outcoupling efficiencyof emitted light.

Discussion of the Related Art

With the development of information society, demands for display devicesdisplaying an image are increasing in various ways. In the field ofdisplay devices, a large-sized cathode ray tube (CRT) has been rapidlyreplaced by a flat panel display (FPD) having advantages of a thinprofile, light weight, and a large-sized screen. Examples of the flatpanel display include a liquid crystal display (LCD), a plasma displaypanel (PDP), an organic light emitting diode (OLED) display, and anelectrophoresis display (EPD).

An OLED display includes self-emitting elements capable of emittinglight by themselves and has advantages of a fast response time, a highemission efficiency, a high luminance, and a wide viewing angle. Inparticular, the OLED display can be manufactured on a flexible plasticsubstrate. In addition, the OLED display has advantages of a lowerdriving voltage, lower power consumption, and better color tone ascompared to a plasma display panel or an inorganic electroluminescentdisplay.

The OLED display is roughly classified into a top emission OLED displayand a bottom emission OLED display depending on an emission direction oflight emitted from an emission layer.

In the bottom emission OLED display, light emitted from an emissionlayer is emitted toward a substrate on which a thin film transistor fordriving an element is formed. On the other hand, in the top emissionOLED display, light emitted from an emission layer is emitted toward aposition opposite a substrate on which a thin film transistor fordriving an element is formed. To this end, the top emission OLED displayincludes a reflective electrode as an anode and a transmissive electrodecapable of transmitting light as a cathode. Thus, light emitted from theemission layer is reflected from the reflective electrode and is emittedto the transmissive electrode. In this instance, light emitted from theemission layer may be totally reflected to the inside of the OLEDdisplay duet to a difference in a refractive index between the cathodehaving a high refractive index and a structure (for example, apassivation layer) on the cathode. The light totally reflected to theinside of the OLED display is trapped inside the OLED display, and thusan outcoupling efficiency of the OLED display is reduced.

Accordingly, studies are being actively carried out to more efficientlyextract light emitted from the OLED display for the improvement of theoutcoupling efficiency.

SUMMARY

The present disclosure provides a display device capable of improving anoutcoupling efficiency of emitted light.

In one embodiment, a display device comprises: a substrate; a subpixelarranged on the substrate, the subpixel including an organic lightemitting diode having an emission portion that emits light; a firstpassivation layer disposed on the organic light emitting diode; at leastone lens positioned on the first passivation layer, the at least onelens disposed in a position corresponding to the emission portion of theorganic light emitting diode; a cover layer covering the at least onelens; and a second passivation layer disposed on the cover layer.

In another embodiment, a display device comprises: a substrate; asubpixel arranged on the substrate, the subpixel including an organiclight emitting diode having an emission portion that emits light; atleast one lens positioned on the organic light emitting diode, the atleast one lens entirely overlapping the emission portion in itsentirety; and a first cover layer on the at least one lens.

In another embodiment, a display device comprises: a plurality of pixelsthat each include a plurality of sub-pixels, each of the plurality ofsub-pixels of at least one pixel including; an emission portion thatemits light; and at least one lens that overlaps the emission portionand comprises a diameter that is at least as wide as width of theemission portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, that may be included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure andtogether with the description serve to explain various principles of thedisclosure.

FIG. 1 is a schematic block diagram of an organic light emitting diode(OLED) display according to an embodiment of the disclosure.

FIG. 2 illustrates a first example of a circuit configuration of asubpixel according to an embodiment of the disclosure.

FIG. 3 illustrates a second example of a circuit configuration of asubpixel according to an embodiment of the disclosure.

FIG. 4 is a cross-sectional view illustrating a subpixel of an OLEDdisplay according to an embodiment of the disclosure.

FIG. 5 is a cross-sectional view of an OLED display according to a firstembodiment of the disclosure.

FIG. 6 is a plan view of an OLED display according to the firstembodiment of the disclosure.

FIG. 7 is a cross-sectional view of an OLED display according to asecond embodiment of the disclosure.

FIG. 8 is a plan view of an OLED display according to the secondembodiment of the disclosure.

FIG. 9 is a cross-sectional view illustrating another configuration ofan OLED display according to the second embodiment of the disclosure.

FIG. 10 is a plan view illustrating another configuration of an OLEDdisplay according to the second embodiment of the disclosure.

FIG. 11 is a cross-sectional view of an OLED display according to athird embodiment of the disclosure.

FIGS. 12 to 17 are cross-sectional views illustrating in stages a methodof manufacturing an OLED display according to a first embodiment of thedisclosure.

FIG. 18 is a graph illustrating an emission intensity depending on aviewing angle in OLED displays manufactured according to a comparativeexample and a first embodiment and a third embodiment of the disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the disclosure,examples of which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts. It will be paid attentionthat detailed description of known arts will be omitted if it isdetermined that the arts can mislead the embodiments of the disclosure.Names of the respective elements used in the following explanations areselected only for convenience of writing the specification and may bethus different from those used in actual products. In the description ofpositional relationships, when a structure is described as beingpositioned “on or above”, “under or below”, “next to” another structure,this description should be construed as including a case in which thestructures directly contact each other as well as a case in which athird structure is disposed therebetween.

A display device according to embodiments of the disclosure is a plasticdisplay device, in which a display element is formed on a flexibleplastic substrate. Examples of the plastic display device include anorganic light emitting diode (OLED) display, a liquid crystal display(LCD), and an electrophoresis display. Embodiments are described usingthe OLED display by way of example. An OLED display includes an emissionlayer, that is formed of an organic material, between a first electrodeserving as an anode and a second electrode serving as a cathode. TheOLED display is a self-emission display device configured to formhole-electron pairs, i.e., excitons, by combining holes received fromthe first electrode and electrons received from the second electrodeinside the emission layer and emit light by energy generated when theexcitons return to a ground level. The OLED display according toembodiments of the disclosure may alternatively use a glass substraterather than the plastic substrate.

In embodiments disclosed herein, pixels of the display device areroughly arranged in a stripe format and a pentile format. In the stripeformat, subpixels RGB or RGBW form a unit pixel, and unit pixels arearranged in the stripe format. In the pentile format, subpixels RG andsubpixels BG each form a unit pixel, and unit pixels of the subpixels RGand BG are alternately arranged. Embodiments of the disclosure describepentile pixels by way of example, but are not limited thereto.Embodiments of the disclosure may use pixels arranged in the stripeformat.

Embodiments of the disclosure are described below with reference toFIGS. 1 to 18.

FIG. 1 is a schematic block diagram of an OLED display according to anembodiment of the disclosure. FIG. 2 illustrates a first example of acircuit configuration of a subpixel according to an embodiment of thedisclosure. FIG. 3 illustrates a second example of a circuitconfiguration of a subpixel according to an embodiment of thedisclosure.

Referring to FIG. 1, an OLED display according to an embodiment of thedisclosure includes an image processing unit 10, a timing controller 20,a data driver 30, a gate driver 40, and a display panel 50.

The image processing unit 10 outputs a data signal DATA and a dataenable signal DE supplied from the outside. The image processing unit 10may output one or more of a vertical sync signal, a horizontal syncsignal, and a clock signal in addition to the data enable signal DE. Forthe sake of brevity and ease of reading, these signals are not shown.The image processing unit 10 may be formed on a system circuit board inan integrated circuit (IC) form.

The timing controller 20 receives the data signal DATA and drivingsignals including the data enable signal DE or the vertical sync signal,the horizontal sync signal, the clock signal, etc. from the imageprocessing unit 10.

The timing controller 20 outputs a gate timing control signal GDC forcontrolling operation timing of the gate driver 40 and a data timingcontrol signal DDC for controlling operation timing of the data driver30 based on the driving signals. The timing controller 20 may be formedon a control circuit board in an IC form.

The data driver 30 samples and latches the data signal DATA receivedfrom the timing controller 20 in response to the data timing controlsignal DDC supplied from the timing controller 20 and converts thesampled and latched data signal DATA using gamma reference voltages. Thedata driver 30 outputs the converted data signal DATA to data lines DL1to DLn. The data driver 30 is attached to a substrate as an IC.

The gate driver 40 outputs a gate signal while shifting a level of agate voltage in response to the gate timing control signal GDC suppliedfrom the timing controller 20. The gate driver 40 outputs the gatesignal to gate lines GL1 to GLm. The gate driver 40 may be formed on agate circuit board in an IC form, or may be formed on the display panel50 in a gate-in panel (GIP) manner.

The display panel 50 displays an image in response to the data signalDATA and the gate signal respectively received from the data driver 30and the gate driver 40. The display panel 50 includes subpixels SPdisplaying an image.

Referring to FIG. 2, each subpixel may includes a switching transistorSW, a driving transistor DR, a compensation circuit CC, and an organiclight emitting diode (OLED). The OLED operates to emit light based on adriving current generated by the driving transistor DR.

The switching transistor SW performs a switching operation so that adata signal supplied through a first data line DL1 is stored in acapacitor Cst as a data voltage in response to a gate signal suppliedthrough a first gate line GL1. The driving transistor DR enables adriving current to flow between a high potential power line VDD and alow potential power line GND based on the data voltage stored in thecapacitor Cst. The compensation circuit CC is a circuit for compensatingfor a threshold voltage of the driving transistor DR. The capacitor Cstconnected to the switching transistor SW or the driving transistor DRmay be mounted inside the compensation circuit CC.

The compensation circuit CC includes one or more thin film transistors(TFTs) and a capacitor. Configuration of the compensation circuit CC maybe variously changed depending on a compensation method. A briefdescription of the compensation circuit CC will be made.

As shown in FIG. 3, the subpixel including the compensation circuit CCmay further include a signal line and a power line for driving acompensation TFT and supplying a predetermined signal or electric power.The added signal line may be defined as a 1-2 gate line GL1 b fordriving the compensation TFT included in the subpixel. In FIG. 3, “GL1a” is a 1-1 gate line for driving the switching transistor SW. The addedpower line may be defined as an initialization power line INIT forinitializing a predetermined node of the subpixel at a predeterminedvoltage. However, embodiments are not limited thereto.

FIGS. 2 and 3 illustrate that one subpixel includes the compensationcircuit CC by way of example. However, the compensation circuit CC maybe omitted when an object (for example, the data driver 30) to becompensated is positioned outside the subpixel. The subpixel has aconfiguration of 2T(Transistor)1C(Capacitor) in which the switchingtransistor SW, the driving transistor DR, the capacitor, and the OLEDare provided. However, when the compensation circuit CC is added to thesubpixel, the subpixel may have various configurations such as 3T1C,4T2C, 5T2C, 6T2C, 7T2C, and the like.

Also, FIGS. 2 and 3 illustrate that the compensation circuit CC ispositioned between the switching transistor SW and the drivingtransistor DR by way of an example. However, the compensation circuit CCmay be further positioned between the driving transistor DR and theOLED. The position and the structure of the compensation circuit CC arenot limited to the ones illustrated in FIGS. 2 and 3.

A cross-sectional structure of a subpixel SP of an OLED displayaccording to an embodiment of the disclosure is described below withreference to FIG. 4.

As shown in FIG. 4, in an OLED display according to an embodiment of thedisclosure, a first buffer layer BUF1 is positioned on a substrate PI.The substrate PI may be formed of plastic and may be, for example, apolyimide. Thus, the substrate PI according to the embodiment of thedisclosure may have flexible characteristics. The first buffer layerBUF1 protects a thin film transistor formed in a subsequent process fromimpurities, for example, alkali ions discharged from the substrate PI.The first buffer layer BUF1 may be formed of a silicon oxide (SiOx)layer, a silicon nitride (SiNx) layer, or a multilayer thereof.

A shield layer LS is positioned on the first buffer layer BUF1. Theshield layer LS prevents a reduction in a panel driving current whichmay be generated by using a polyimide substrate. A second buffer BUF2 ispositioned on the shield layer LS. The second buffer BUF2 protects athin film transistor formed in a subsequent process from impurities, forexample, alkali ions discharged from the shield layer LS. The secondbuffer layer BUF2 may be formed of a silicon oxide (SiOx) layer, asilicon nitride (SiNx) layer, or a multilayer thereof.

An active layer ACT is positioned on the second buffer layer BUF2 andmay be formed of a silicon semiconductor or an oxide semiconductor. Thesilicon semiconductor may include amorphous silicon or crystallizedpolycrystalline silicon. The polycrystalline silicon has high mobility(for example, more than 100 cm²/Vs), low power consumption, andexcellent reliability. Thus, the polycrystalline silicon can be appliedto a gate driver and/or a multiplexer (MUX) for use in a driving elementor applied for a driving TFT of each pixel of the OLED display. Becausethe oxide semiconductor has a low OFF-current, the oxide semiconductoris suitable for a switching TFT which has a short ON-time and a longOFF-time. Further, because the oxide semiconductor increases a voltagehold time of the pixel due to the low OFF-current, the oxidesemiconductor is suitable for a display device requiring a low-speeddrive and/or low power consumption. In addition, the active layer ACTincludes a drain region and a source region each including p-type orn-type impurities, and also includes a channel region between the drainregion and the source region.

A gate insulating layer GI is positioned on the active layer ACT and maybe formed of a silicon oxide (SiOx) layer, a silicon nitride (SiNx)layer, or a multilayer thereof. A gate electrode GA is positioned on thegate insulating layer GI at a location corresponding to a predeterminedregion (i.e., the channel region when impurities are injected) of theactive layer ACT. The gate electrode GA may be formed of one ofmolybdenum (Mo), aluminum (Al), chrome (Cr), gold (Au), titanium (Ti),nickel (Ni), neodymium (Nd), copper (Cu), or a combination thereof.Further, the gate electrode GA may be a multilayer formed of one ofmolybdenum (Mo), aluminum (Al), chrome (Cr), gold (Au), titanium (Ti),nickel (Ni), neodymium (Nd), copper (Cu), or a combination thereof. Forexample, the gate electrode GA may be formed as a double layer ofMo/AlNd or Mo/Al.

An interlayer dielectric layer ILD is positioned on the gate electrodeGA and insulates the gate electrode GA. The interlayer dielectric layerILD may be formed of a silicon oxide (SiOx) layer, a silicon nitride(SiNx) layer, or a multilayer thereof. Contact holes CH exposing aportion of the active layer ACT are formed at a portion where each ofthe interlayer dielectric layer ILD and the gate insulating layer GI isformed.

A drain electrode DE and a source electrode SE are positioned on theinterlayer dielectric layer ILD. The drain electrode DE is connected tothe active layer ACT through the contact hole CH exposing the drainregion of the active layer ACT, and the source electrode SE is connectedto the active layer ACT through the contact hole CH exposing the sourceregion of the active layer ACT. Each of the source electrode SE and thedrain electrode DE may be formed as a single layer or as a multilayer.When each of the source electrode SE and the drain electrode DE isformed as the single layer, each of the source electrode SE and thedrain electrode DE may be formed of one of molybdenum (Mo), aluminum(Al), chrome (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium(Nd), copper (Cu), or a combination thereof. When each of the sourceelectrode SE and the drain electrode DE is formed as the multilayer,each of the source electrode SE and the drain electrode DE may be formedas a double layer of Mo/Al—Nd or as a triple layer of Ti/Al/Ti, Mo/Al/Moor Mo/Al-Nd/Mo.

Accordingly, a thin film transistor TFT including the active layer ACT,the gate electrode GA, the source electrode SE, and the drain electrodeDE is formed.

Further, an inorganic layer IOL is positioned on the substrate PIincluding the thin film transistor TFT. The inorganic layer IOL is aninsulating layer protecting the component underlying the inorganic layerIOL and may be a silicon oxide (SiOx) layer, a silicon nitride (SiNx)layer, or a multilayer thereof. An overcoat layer OC is positioned onthe inorganic layer IOL. The overcoat layer OC may be a planarizationlayer for reducing a height difference of an underlying structure andmay be formed of an organic material such as polyimide,benzocyclobutene-based resin, and acrylate. For example, the overcoatlayer OC may be formed through a spin-on glass (SOG) method for coatingthe organic material in a liquid state and then curing the organicmaterial.

A via hole VIA exposing the drain electrode DE of the thin filmtransistor TFT is positioned in a portion of the overcoat layer OC. Anorganic light emitting diode OLED is positioned on the overcoat layerOC. More specifically, a first electrode ANO is positioned on theovercoat layer OC. The first electrode ANO serves as a pixel electrodeand is connected to the drain electrode DE of the thin film transistorTFT through the via hole VIA. The first electrode ANO is an anode andmay be formed of a transparent conductive material such as indium tinoxide (ITO), indium zinc oxide (IZO), and zinc oxide (ZnO). When thefirst electrode ANO is a reflective electrode, the first electrode ANOmay further include a reflective layer. The reflective layer may beformed of aluminum (Al), copper (Cu), silver (Ag), nickel (Ni),palladium (Pd) or a combination thereof. For example, the reflectivelayer may be formed of an Ag/Pd/Cu (APC) alloy.

In addition, a bank layer BNK defining pixels is positioned on thesubstrate PI including the first electrode ANO. The bank layer BNK maybe formed of an organic material such as polyimide,benzocyclobutene-based resin, and acrylate. The bank layer BNK includesa pixel definition portion exposing the first electrode ANO. An emissionlayer EML contacting the first electrode ANO is positioned in the pixeldefinition portion of the bank layer BNK. The emission layer EML atleast includes a layer in which electrons and holes combine and emitlight. A hole injection layer and/or a hole transport layer may bepositioned between the emission layer EML and the first electrode ANO,and an electron injection layer and/or an electron transport layer maybe positioned between the emission layer EML and a second electrode CAT.

The second electrode CAT is positioned on the emission layer EML and maybe positioned on an entire surface of a display area. In addition, thesecond electrode CAT is a cathode electrode and may be formed ofmagnesium (Mg), calcium (Ca), aluminum (Al), silver (Ag), or acombination thereof each having a low work function. When the secondelectrode CAT is a transmissive electrode, the second electrode CAT maybe thin enough to transmit light. Further, when the second electrode CATis a reflective electrode, the second electrode CAT may be thick enoughto reflect light.

The OLED display according to embodiments of the disclosure may includea lens on a path of light emitted from an emission layer, in order toprevent light emitted from the emission layer from being damaged bytotal reflection of the light. In the following description, adescription of the components below the organic light emitting diodeshown in FIG. 4 is omitted, and configuration of the components on theorganic light emitting diode is described in detail.

First Embodiment

FIG. 5 is a cross-sectional view of an OLED display according to a firstembodiment of the disclosure. FIG. 6 is a plan view of an OLED displayaccording to the first embodiment of the disclosure.

Referring to FIG. 5, an OLED display according to a first embodiment ofthe disclosure forms a first passivation layer PAS1 on an organic lightemitting diode to protect the organic light emitting diode from asubsequent process or moisture. The OLED display includes a lens LEN onthe first passivation layer PAS1, and the lens LEN can upwardlyconcentrate a light path. The lens LEN will be described in detaillater. A cover layer PCL is positioned on the first passivation layerPAS1 including the lens LEN. The cover layer PCL functions to make upfor a height difference of an underlying structure. For example, thecover layer PCL can make up for a height difference resulting from thelens LEN or foreign substances which may be present. The cover layer PCLmay have a thickness of 5 μm to 20 μm capable of making up for theheight difference. The cover layer PCL may be formed of the same organicmaterial as a bank layer BNK described above. A second passivation layerPAS2 is disposed on the cover layer PCL and protects an underlyingstructure.

The lens LEN is disposed corresponding to an emission portion LEP of theorganic light emitting diode. The emission portion LEP of the organiclight emitting diode is an area where light is emitted from an emissionlayer EML. More specifically, the emission portion LEP may be an areawhere a first electrode ANO and the emission layer EML contact eachother. The lens LEN is disposed to entirely cover the emission portionLEP of the organic light emitting diode. Further, the lens LEN isconfigured such that all of light emitted from the emission portion LEPcan be received inside the lens LEN.

(a) of FIG. 6 illustrates that R, G, B and G subpixels SP are arrangedin a pentile format, and (b) of FIG. 6 illustrates that R, G and Bsubpixels SP are arranged in a stripe format. As described above, thelens LEN according to the embodiment of the disclosure may be disposedto entirely cover an emission portion LEP of each subpixel SP. Morespecifically, the lenses LEN respectively correspond to the emissionportions LEP of the subpixels SP, and thus one lens LEN is disposed tocover an emission portion LEP of one subpixel SP. The lens LEN does notinvade other subpixel SP adjacent to the lens LEN, and the lenses LENare spaced from one another. In some embodiments, the shape of theemission portion LEP is a polygon, and the shape of the lens LEN is acircle.

Referring again to FIG. 5, the lens LEN according to the embodiment ofthe disclosure has enough size to cover the emission portion LEP. Morespecifically, a diameter L1 of the lens LEN is greater than a width W1of the emission portion LEP, and thus the lens LEN can entirely coverthe emission portion LEP. In embodiments disclosed herein, the width W1of the emission portion LEP indicates a maximum width of the emissionportion LEP.

A height L2 of the lens LEN is equal to or less than the diameter L1 ofthe lens LEN. More specifically, the height L2 of the lens LEN is 0.3 to1 times the diameter L1 of the lens LEN. When the height L2 of the lensLEN is more than 0.3 times the diameter L1 of the lens LEN, a curvedangle of the lens LEN increases. Hence, an outcoupling efficiency can beimproved by upwardly concentrating light. Further, when the height L2 ofthe lens LEN is less than 1 times the diameter L1 of the lens LEN, amanufacturing process can be prevented from being difficult due to anexcessive increase in the height L2 of the lens LEN. In particular, whena ratio of the height L2 of the lens LEN to the diameter L1 of the lensLEN is 0.5:1, an effect of the lens LEN may be the most effective. Forexample, the diameter L1 of the lens LEN according to the embodiment ofthe disclosure may be 10 μm to 30 μm, and the height L2 of the lens LENmay be 3 μm to 30 μm.

The embodiment of the disclosure differently sets a refractive index ofthe lens LEN and a refractive index of the cover layer PCL, in order tochange a light path at an interface between the lens LEN and the coverlayer PCL. Light emitted from the emission layer EML is incident on thelens LEN and is refracted at the interface between the lens LEN and thecover layer PCL due to a difference between the refractive index of thelens LEN and the refractive index of the cover layer PCL. Hence, a pathof the light emitted from the emission layer EML is changed. Inembodiments disclosed herein, a refractive index N1 of the lens LEN maybe set to be greater than a refractive index N2 of the cover layer PCL.For example, the refractive index N1 of the lens LEN may be greater thanthe refractive index N2 of the cover layer PCL by 0.1 to 1. When therefractive index N1 of the lens LEN is greater than the refractive indexN2 of the cover layer PCL by 0.1 or more, light can be refracted at theinterface between the lens LEN and the cover layer PCL and can beupwardly concentrated. Hence, the outcoupling efficiency can beimproved. Further, when the refractive index N1 of the lens LEN isgreater than the refractive index N2 of the cover layer PCL by 1 orless, light can be prevented from being excessively refracted at theinterface between the lens LEN and the cover layer PCL and being lost atthe side. For example, the refractive index N1 of the lens LEN may be1.73, and the refractive index N2 of the cover layer PCL may be 1.52.

The lens LEN according to the embodiment of the disclosure is disposedadjacent to the emission layer EML. A second electrode CAT contactingthe emission layer EML and the first passivation layer PAS1 contactingthe second electrode CAT are disposed between the emission layer EML andthe lens LEN. The lens LEN is disposed on the first passivation layerPAS1 and contacts the first passivation layer PAS1.

Light emitted from the emission layer EML may be considerably lostbetween the emission layer EML and the second electrode CAT and betweenthe second electrode CAT and the first passivation layer PAS1. Thus, theembodiment of the disclosure can reduce a loss of emitted light bydisposing the lens LEN as close as possible to the emission layer EML.To this end, a distance between an upper surface of the emission layerEML and a lower surface of the lens LEN may be 100 nm to 10,000 nm. Thedistance between the upper surface of the emission layer EML and thelower surface of the lens LEN may be substantially equal to a sum ofthicknesses of the second electrode CAT and the first passivation layerPAS1. When the distance between the upper surface of the emission layerEML and the lower surface of the lens LEN is equal to or greater than100 nm, each of the second electrode CAT and the first passivation layerPAS1 between the emission layer EML and the lens LEN can have athickness that facilitates performing a function. Further, when thedistance between the upper surface of the emission layer EML and thelower surface of the lens LEN is equal to or less than 10,000 nm, lightcan be prevented from being lost due to a very long distance between theemission layer EML and the lens LEN. More preferably, but not required,the distance between the upper surface of the emission layer EML and thelower surface of the lens LEN may be 500 nm to 2,000 nm. Hence, theembodiment of the disclosure can prevent a loss of light emitted fromthe emission layer EML.

A portion of the lens LEN contacts the second passivation layer PAS2. Asshown in FIG. 5, a portion of an upper surface of the lens LEN maycontact the second passivation layer PAS2. A contact area SQ between thelens LEN and the second passivation layer PAS2 is an area on which lightemitted from the emission layer EML is vertically incident. If apassivation layer, has a large difference in a refractive index betweenthe passivation layer and the lens LEN, is formed in the contact areaSQ, light is again reflected in an incident direction and is hardlyextracted to the outside. Thus, the lens LEN contacts the secondpassivation layer PAS2 having a refractive index similar to therefractive index of the lens LEN in the contact area SQ and thus cantransmit light. To this end, a difference in the refractive indexbetween the lens LEN and the second passivation layer PAS2 may be lessthan 0.3. Although an occupation rate of each subpixel occupied by thecontact area SQ between the lens LEN and the second passivation layerPAS2 is not large, the occupation rate in all the subpixels included inthe OLED display is not small. Thus, the contact area SQ can greatlycontribute to the improvement of the outcoupling efficiency.

As described above, the OLED display according to the first embodimentof the disclosure includes the lens LEN corresponding to the emissionportion LEP on the organic light emitting diode and upwardly refractslight emitted from the emission layer EML through the lens LEN, therebyimproving the outcoupling efficiency.

Second Embodiment

FIG. 7 is a cross-sectional view of an OLED display according to asecond embodiment of the disclosure. FIG. 8 is a plan view of an OLEDdisplay according to the second embodiment of the disclosure. FIG. 9 isa cross-sectional view illustrating another configuration of an OLEDdisplay according to the second embodiment of the disclosure. FIG. 10 isa plan view illustrating another configuration of an OLED displayaccording to the second embodiment of the disclosure.

Referring to FIGS. 7 and 8, an OLED display according to a secondembodiment of the disclosure includes a lens LEN on a first passivationlayer PAS1, and the lens LEN can upwardly concentrate a light path. Thelens LEN is disposed corresponding to an emission portion LEP of anorganic light emitting diode and covers the emission portion LEP of theorganic light emitting diode. In this instance, a diameter L1 of thelens LEN may be substantially equal to a width W1 of the emissionportion LEP. Thus, because the lens LEN covers the emission portion LEPthrough a minimum diameter of the lens LEN, a thickness of the OLEDdisplay can be prevented from increasing due to an increase in a size ofthe lens LEN. As a result, the manufacturing cost of the OLED displaycan be reduced. In some embodiments, the shape of the emission portionLEP is a polygon, and the shape of the lens LEN is a circle.

On the other hand, referring to FIG. 9, two or more lenses LEN may bedisposed corresponding to the emission portion LEP of the organic lightemitting diode. The two or more lenses LEN are disposed to cover theemission portion LEP of the organic light emitting diode. A sum ofdiameters L1 of the two or more lenses LEN may be equal to or greaterthan a width W1 of the emission portion LEP.

For example, as shown in (a) of FIG. 10, two lenses LEN may be disposedcorresponding to one emission portion LEP. Alternatively, as shown in(b) of FIG. 10, four lenses LEN may be disposed corresponding to oneemission portion LEP. FIG. 10 merely illustrates examples of the presentdisclosure, and thus the number and the arrangement of lenses may bevariously changed. In some embodiments, the shape of the emissionportion LEP is a polygon, and the shape of the lens LEN is a circle.

As shown in FIG. 9, light emitted from an emission layer EML isextracted to the outside through a predetermined light path LP. Forexample, light emitted from the emission layer EML is upwardly refractedat an interface between a left lens LEN and a passivation layer PCL dueto a difference between a high refractive index of the left lens LEN anda low refractive index of the passivation layer PCL and then travelstoward the inside of the passivation layer PCL. The light travelingtoward the inside of the passivation layer PCL is refracted to the rightat an interface between a right lens LEN and the passivation layer PCLdue to a difference between a high refractive index of the right lensLEN and the low refractive index of the passivation layer PCL and thentravels toward the inside of the lens LEN. Subsequently, the lighttraveling toward the inside of the lens LEN is upwardly refracted at aninterface between the lens LEN and the passivation layer PCL due to adifference between the high refractive index of the lens LEN and the lowrefractive index of the passivation layer PCL and then is extracted.Thus, when the plurality of lenses is provided as described above, lightemitted from the emission layer EML is upwardly refracted again comparedto when one lens is provided. Hence, outcoupling efficiency can befurther improved.

The second embodiment of the disclosure describes that the diameter ofthe lens is equal to the width of the emission portion, or the pluralityof lenses is provided. As a result, the second embodiment of thedisclosure can further improve the outcoupling efficiency throughvarious configurations of the lenses.

Third Embodiment

FIG. 11 is a cross-sectional view of an OLED display according to athird embodiment of the disclosure.

Referring to FIG. 11, a lamination structure of components laminated ona lens LEN in the third embodiment of the disclosure is different fromthat in the first and second embodiments.

More specifically, a first cover layer PCL1 is positioned on a firstpassivation layer PAS1. The first cover layer PCL1 functions to make upfor a height difference of an underlying structure. For example, thefirst cover layer PCL1 can make up for a height difference resultingfrom foreign substances which may be present. A second passivation layerPAS2 is disposed on the first cover layer PCL1 and protects anunderlying structure. The lens LEN is disposed on the second passivationlayer PAS2, and a second cover layer PCL2 is disposed to include thelens LEN. A third passivation layer PAS3 is disposed on the second coverlayer PCL2 and protects an underlying structure.

The lens LEN according to the third embodiment of the disclosure isdisposed on the first cover layer PCL1 and the second passivation layerPAS2 and thus can prevent an organic light emitting diode from beingdamaged in a process for manufacturing the lens LEN. Further, becausethe first cover layer PCL1 makes up for the height difference resultingfrom foreign substances which may be present, the first cover layer PCL1can prevent the lens LEN from being formed at the foreign substances andcan improve outcoupling efficiency.

A method of manufacturing the OLED display according to the embodimentsof the disclosure is described below using the OLED display according tothe first embodiment of the disclosure as an example.

FIGS. 12 to 17 are cross-sectional views illustrating in stages a methodof manufacturing the OLED display according to the first embodiment ofthe disclosure.

Referring to FIG. 12, an organic light emitting diode OLED is formed onan overcoat layer OC. More specifically, a first electrode ANO servingas a reflective electrode is positioned on the overcoat layer OC, and anorganic material such as polyimide, benzocyclobutene-based resin, andacrylate is coated on the first electrode ANO to form a bank layer BNK.An emission layer EML is deposited on the bank layer BNK, and magnesium(Mg), calcium (Ca), aluminum (Al), silver (Ag), or a combination thereofeach having a low work function is deposited on the emission layer EMLto form a second electrode CAT.

Next, a silicon oxide (SiOx) layer, a silicon nitride (SiNx) layer, or amultilayer thereof is deposited on the second electrode CAT to form afirst passivation layer PAS1. An organic material such as polyimide,benzocyclobutene-based resin, and acrylate is coated on the firstpassivation layer PAS1 to form a coating layer PCM. The coating layerPCM may use known materials in addition to the above-describedmaterials. A photoresist PR is coated on the coating layer PCM.

Next, referring to FIG. 13, the photoresist PR is developed in a shapeof a lens to be formed. Thus, a photoresist pattern PRP of the lensshape is formed as in a scanning electron microscope (SEM) photograph ofFIG. 14.

Next, referring to FIG. 15, the coating layer PCM is etched using thedeveloped photoresist pattern PRP, and the photoresist pattern PRP isremoved, thereby forming a lens LEN. Thus, the lens LEN is formed as ina SEM photograph of FIG. 16.

Next, referring to FIG. 17, an organic material such as polyimide,benzocyclobutene-based resin, and acrylate is coated on the firstpassivation layer PAS1, on which the lens LEN is formed, to form a coverlayer PCL. In this instance, a formation material of the lens LEN and aformation material of the cover layer PCL have different refractiveindexes, and a refractive index of the lens LEN is greater than arefractive index of the cover layer PCL.

Finally, a silicon oxide (SiOx) layer, a silicon nitride (SiNx) layer,or a multilayer thereof is deposited on the cover layer PCL to form thefirst passivation layer PAS1. As a result, the OLED display according tothe embodiments of the disclosure is manufactured.

FIG. 18 is a graph illustrating an emission intensity depending on aviewing angle in OLED displays manufactured according to a comparativeexample and the first embodiment and the third embodiment of thedisclosure. In FIG. 18, the comparative example has a structure in whichthe lens is removed in the OLED display according to the firstembodiment of the disclosure.

Referring to FIG. 18, an emission intensity of the OLED display notincluding the lens in accordance with the comparative example was about0.6. On the other hand, an emission intensity of the OLED displayincluding the lens in accordance with the first embodiment of thedisclosure was about 1.0. Further, an emission intensity of the OLEDdisplay further including the cover layer below the lens in accordancewith the first embodiment of the disclosure was about 0.85.

It could be seen from the graph of FIG. 18 that the emission intensitywas improved by an outcoupling effect when the lens was included in theOLED display.

As described above, the OLED display according to the embodiments of thedisclosure includes the lens corresponding to the emission portion onthe organic light emitting diode and upwardly refracts light emittedfrom the emission layer through the lens, thereby improving theoutcoupling efficiency.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the scope of the principles of thisdisclosure. More particularly, various variations and modifications arepossible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A display device comprising: a substrate; asubpixel arranged on the substrate, the subpixel including an organiclight emitting diode having an emission portion that emits light; afirst passivation layer disposed on the organic light emitting diode; atleast one lens positioned on the first passivation layer, the at leastone lens disposed in a position corresponding to the emission portion ofthe organic light emitting diode; a cover layer covering the at leastone lens; and a second passivation layer disposed on the cover layer. 2.The display device of claim 1, wherein the organic light emitting diodeincludes: a first electrode; an emission layer disposed on the firstelectrode; and a second electrode disposed on the emission layer.
 3. Thedisplay device of claim 2, wherein the first electrode is in contactwith the emission layer in the emission portion.
 4. The display deviceof claim 1, wherein the at least one lens overlaps the emission portionin its entirety.
 5. The display device of claim 1, wherein a diameter ofthe at least one lens is equal to or greater than a width of theemission portion.
 6. The display device of claim 1, wherein a height ofthe at least one lens is equal to or less than a diameter of the atleast one lens.
 7. The display device of claim 1, wherein a refractiveindex of the at least one lens is greater than a refractive index of thecover layer.
 8. The display device of claim 2, wherein the firstpassivation layer is in contact with the second electrode, and the atleast one lens is in contact with the first passivation layer.
 9. Adisplay device comprising: a substrate; a subpixel arranged on thesubstrate, the subpixel including an organic light emitting diode havingan emission portion that emits light; at least one lens positioned onthe organic light emitting diode, the at least one lens entirelyoverlapping the emission portion in its entirety; and a first coverlayer on the at least one lens.
 10. The display device of claim 9,wherein the organic light emitting diode includes: a first electrode; anemission layer disposed on the first electrode, wherein the firstelectrode is in contact with the emission layer in the emission portion;and a second electrode disposed on the emission layer.
 11. The displaydevice of claim 9, wherein the at least one lens comprises a singlelens, a diameter of the single lens is equal to or greater than a widthof the emission portion.
 12. The display device of claim 9, wherein theat least one lens comprises a plurality of lenses, each of the pluralityof lenses comprises a diameter and a sum of diameters of the pluralityof lenses is equal to or greater than a width of the emission portion.13. The display device of claim 9, wherein a height of the at least onelens is equal to or less than a diameter of the at least one lens. 14.The display device of claim 9, wherein a refractive index of the atleast one lens is greater than a refractive index of the first coverlayer.
 15. The display device of claim 9, further comprising: a firstpassivation layer on the organic light emitting diode; and a secondpassivation layer on the at least one lens; wherein the at least onelens is between the first passivation layer and the second passivationlayer.
 16. The display device of claim 9, further comprising: a firstpassivation layer on the organic light emitting diode; a second coverlayer on the first passivation layer; a second passivation layer on thesecond cover layer; and a third passivation layer on the at least onelens; wherein the at least one lens is between the second passivationlayer and the third passivation layer.
 17. A display device comprising:a plurality of pixels that each include a plurality of sub-pixels, eachof the plurality of sub-pixels of at least one pixel including: anemission portion that emits light; and at least one lens that overlapsthe emission portion and comprises a diameter that is at least as wideas a width of the emission portion.
 18. The display device of claim 17,wherein a first subset of the plurality of sub-pixels of at least onepixel is arranged in a first row of sub-pixels and a second subset ofthe plurality of sub pixels of the at least one pixel is arranged in asecond row of sub-pixels that is adjacent to the first row.
 19. Thedisplay device of claim 17, wherein the plurality of sub-pixels of atleast one pixel are arranged in a single row of sub-pixels.
 20. Thedisplay device of claim 17, wherein a shape of the emission portion is apolygon and the shape of the at least one lens is a circle.